Multipurpose Thermal Power Plant System

ABSTRACT

To provide a multipurpose thermal power plant system capable of capturing moisture and carbon dioxide in large quantities at a low cost from exhaust gas of an oxygen combustion boiler. 
     To use an oxygen combustion boiler  1,  an oxygen separator  6,  a coal fuel feed apparatus  7,  a steam turbine  2,  a generator  3,  denitrification equipment  10,  a gas heat exchanger  11,  a condensate cooler  12  for cooling exit gas of the gas heat exchanger with a condensate at an exit of a condenser which is a part of steam cycle water of the turbine, a dust collector  13,  a desulfurizer  14,  a cooling water-desalination apparatus  15,  and a carbon dioxide liquefier  16,  to utilize the characteristic that main components of exhaust gas of the oxygen combustion boiler  1  after combustion are carbon dioxide gas and steam, and to simultaneously capture moisture and carbon dioxide in the gas by cooling and compressing the exhaust gas. And to install a water feed system for utilizing the captured moisture as cycle water of a steam-water cycle of the steam turbine.

CLAIM OF PRIORITY

The present application claims priority from Japanese patent applicationJP 2010-210356 filed on Sep. 21, 2010, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a multipurpose thermal power plantsystem and more particularly to a fossil fuel combustion multipurposethermal power plant system having a function for simultaneouslyperforming the three great functions of water desalination, carbondioxide capture, and power generation, or simultaneously performing thepower generation function and water desalination function or carbondioxide capture function.

2. Description of Related Art

A thermal power plant having the water desalination function forbleeding steam from the steam turbine cycle for generating power,thereby producing fresh water from seawater is already put intopractical use. Furthermore, a coal fuel combustion thermal power plantsystem simultaneously including not only the power generation functionand water desalination function but also a function for compressing andcooling carbon dioxide included in the boiler exhaust gas of an oxygencombustion boiler, thereby capturing carbon dioxide is devised. Forexample, in Japanese Patent Laid-open No. 2010-101587 (Patent document1), in a thermal power plant system including an oxygen combustionboiler, an oxygen separator, a coal feed apparatus, a steam turbine, anda steam turbine generator for utilizing that the main components of theexhaust gas of the oxygen combustion boiler are carbon dioxide andsteam, using denitrification equipment, an oxygen preheater, a dustcollector, a desulfurizer, cooling and dehumidification equipment, and acarbon dioxide liquefier, the constitution of a coal combustion andoxygen combustion boiler for cooling exhaust gas, removing moisture inthe exhaust gas, and then capturing carbon dioxide and the controlmethod for the oxygen combustion boiler are disclosed.

Patent document 1: Japanese Patent Laid-open No. 2010-101587

SUMMARY OF THE INVENTION

In Patent document 1, moisture generated by the cooling anddehumidification equipment is discharged outside the system. Regardingit, it is inferred that the quantity of moisture generated by thecooling and dehumidification equipment is not sufficient for effectiveuse.

The main components of the exhaust gas from the oxygen combustion boilerare carbon dioxide gas and steam. Namely, when inputting oxygen gas inthe air into the boiler as an oxygen source for boiler fuel, unlike aconventional air combustion boiler forced to input a large amount ofunnecessary nitrogen gas in the air which does not contribute tocombustion into the boiler simultaneously with oxygen gas in the air, inthe case of the oxygen combustion boiler, only oxygen from an exclusiveoxygen generation apparatus is used as a combustion oxygen source of theboiler, so that in the boiler exhaust gas components, steam and carbondioxide which are produced due to oxidation of hydrogen, carbon, andhydrocarbon which are the main components of the fuel are the maincomponents and excessive nitrogen gas in the air is not included.

Thus, the exhaust gas is cooled and compressed, thereby moisture andcarbon dioxide in the gas can be captured simultaneously. A large amountof moisture is included in the exhaust gas of the oxygen combustionboiler, though moisture generated by the conventional cooling anddehumidification equipment is not in a large amount, thus a large amountof moisture in the exhaust gas is discharged outside the system withoutbeing used effectively. If moisture obtained by cooling the exhaust gascan be captured in a large amount at a low cost, the captured moisturecan be utilized as cycle water of the steam-water cycle of the steamturbine. However, in the conventional system, the amount of watercaptured is not sufficient for utilization as cycle water of thesteam-water cycle of the steam turbine.

An object of the present invention is to provide a multipurpose thermalpower plant system capable of capturing moisture and carbon dioxide inlarge quantities at a low cost from the exhaust gas of the oxygencombustion boiler.

The multipurpose thermal power plant system of the present invention,when using fossil fuel composed of carbon, hydrogen, a very small amountof sulfur, and nitrogen as fuel, includes an oxygen combustion boiler, asteam turbine, a generator, an oxygen separator for generating oxygenfed to the oxygen combustion boiler, a fuel feed apparatus for feedingfossil fuel composed of carbon, hydrogen, a very small amount of sulfur,and nitrogen to the oxygen combustion boiler, denitrification equipmentfor removing nitrogen oxide in the exhaust gas of the oxygen combustionboiler, a gas heat exchanger for performing heat exchange between boilerexhaust gas and recirculation boiler exhaust gas including oxygen, acondensate cooler for cooling exhaust gas at the exit of the gas heatexchanger with condensate of the steam turbine, a recirculation systemfor recirculating boiler exhaust gas at the exit of the condensatecooler to the oxygen combustion boiler, an oxygen injection system forfeeding oxygen from the oxygen separator to the recirculation system, adust collector for removing dust from exhaust gas at the exit of thecondensate cooler, a desulfurizer for removing sulfur in the boilerexhaust gas from the dust collector, a cooling water-desalinationapparatus for producing water by cooling boiler exhaust gas from thedesulfurizer, a carbon dioxide liquefier for obtaining carbon dioxide bycompressing boiler exhaust gas at the exit of the coolingwater-desalination apparatus, a carbon dioxide storage tank for storingliquefied carbon dioxide obtained by the carbon dioxide liquefier, afresh water tank for capturing water generated by the coolingwater-desalination apparatus, and a water feed system for feeding waterof the fresh water tank to the steam turbine system as steam cycle waterof the steam turbine.

When using fossil fuel such as liquefied natural gas composed of carbonand hydrogen as fuel, the multipurpose thermal power plant system of thepresent invention includes an oxygen combustion boiler, a steam turbine,a generator, an oxygen separator for generating oxygen fed to the oxygencombustion boiler, a fuel feed apparatus for feeding fossil fuel such asliquefied natural gas composed of carbon and hydrogen to the oxygencombustion boiler, a gas heat exchanger for performing heat exchangebetween boiler exhaust gas and recirculation boiler exhaust gasincluding oxygen, a condensate cooler for cooling exhaust gas at theexit of the gas heat exchanger with condensate of the steam turbine, arecirculation system for recirculating boiler exhaust gas at the exit ofthe condensate cooler to the oxygen combustion boiler, an oxygeninjection system for feeding oxygen from the oxygen separator to therecirculation system, a cooling water-desalination apparatus forproducing water by cooling boiler exhaust gas from the condensatecooler, a carbon dioxide liquefier for obtaining carbon dioxide bycompressing boiler exhaust gas at the exit of the coolingwater-desalination apparatus, a carbon dioxide storage tank for storingliquefied carbon dioxide obtained by the carbon dioxide liquefier, afresh water tank for capturing water generated by the coolingwater-desalination apparatus, and a water feed system for feeding waterof the fresh water tank to the steam turbine system as steam cycle waterof the steam turbine.

When using hydrogen fuel as fuel, the multipurpose thermal power plantsystem of the present invention includes an oxygen combustion boiler, asteam turbine, a generator, an oxygen separator for generating oxygenfed to the oxygen combustion boiler, a fuel feed apparatus for feedinghydrogen fuel to the oxygen combustion boiler, a gas heat exchanger forperforming heat exchange between boiler exhaust gas and recirculationboiler exhaust gas including oxygen, a condensate cooler for coolingexhaust gas at the exit of the gas heat exchanger with condensate of thesteam turbine, a recirculation system for recirculating boiler exhaustgas at the exit of the condensate cooler to the oxygen combustionboiler, an oxygen injection system for feeding oxygen from the oxygenseparator to the recirculation system, a cooling water-desalinationapparatus for producing water by cooling boiler exhaust gas from thecondensate cooler, a fresh water tank for capturing water generated bythe cooling water-desalination apparatus, and a water feed system forfeeding water of the fresh water tank to the steam turbine system assteam cycle water of the steam turbine.

When using fossil fuel composed of carbon as fuel, the multipurposethermal power plant system of the present invention includes an oxygencombustion boiler, a steam turbine, a generator, an oxygen separator forgenerating oxygen fed to the oxygen combustion boiler, a fuel feedapparatus for feeding fossil fuel composed of carbon to the oxygencombustion boiler, a gas heat exchanger for performing heat exchangebetween boiler exhaust gas and recirculation boiler exhaust gasincluding oxygen, a condensate cooler for cooling exhaust gas at theexit of the gas heat exchanger with condensate of the steam turbine, arecirculation system for recirculating boiler exhaust gas at the exit ofthe condensate cooler to the oxygen combustion boiler, an oxygeninjection system for feeding oxygen from the oxygen separator to therecirculation system, a carbon dioxide liquefier for obtaining carbondioxide by compressing boiler exhaust gas from the condensate cooler,and a carbon dioxide storage tank for storing liquefied carbon dioxideobtained by the carbon dioxide liquefier.

According to the present invention, in correspondence to the fuel kindburned by the boiler, from the fuel, not only electric energy but alsowater or carbon dioxide can be obtained simultaneously in largequantities at a low cost by a method friendly to the naturalenvironment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the multipurpose thermal power plant systemof a first embodiment of the present invention using fuel like coalincluding carbon, hydrogen, ash, and moisture as main components ofboiler fuel and a small amount of sulfur and nitrogen;

FIG. 2 is a block diagram of the multipurpose thermal power plant systemof a second embodiment of the present invention using fuel likeliquefied natural gas including carbon, hydrogen, and hydrocarbon asmain components of boiler fuel but not including a small amount ofsulfur and nitrogen;

FIG. 3 is a block diagram of the multipurpose thermal power plant systemof a third embodiment of the present invention using hydrogen gas fuelincluding only hydrogen as a main component of boiler fuel but notincluding a small amount of sulfur and nitrogen; and

FIG. 4 is a block diagram of the multipurpose thermal power plant systemof a fourth embodiment of the present invention using carbon fuelincluding only carbon as a main component of boiler fuel but notincluding a small amount of sulfur and nitrogen.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, by referring to the accompanying drawings, with respect tothe multipurpose thermal power plant system using the oxygen combustionboiler, a plurality of embodiments of the present invention with thefuel of the oxygen combustion boiler changed will be explained. FIGS. 1to 4 show embodiments of the multipurpose thermal power plant systemcorresponding to four kinds of fuel. In all the drawings, the samecomponents are given the same numerals.

Embodiment 1

FIG. 1 shows a first embodiment of the present invention of themultipurpose thermal power plant system using fuel like coal composed ofthe main components of carbon, hydrogen, ash, and moisture as fuel of anoxygen combustion boiler 1 including a very small amount of sulfur andnitrogen. This embodiment is a multipurpose thermal power plant systemfor simultaneously capturing electric power, water, and carbon dioxide.

The multipurpose thermal power plant system of this embodiment includesthe oxygen combustion boiler 1 for burning coal and generating steam, asteam turbine 2 driven so as to rotate by the steam generated by theoxygen combustion boiler 1, an oxygen combustion boiler steam pipe 4 forcarrying steam 51 generated by the oxygen combustion boiler 1, agenerator 3 for converting the turning force of the steam turbine 2 toelectric power, a condensate pump 61 and a feed water pump 66 forfeeding condensate obtained by condensing the steam for driving torotate the steam turbine 2 to water by a condenser 60 to the oxygencombustion boiler 1, and a low-pressure feed water heater 62 and ahigh-pressure feed water heater 67 for heating the condensate by bleedsteam from the steam turbine 2.

The condensate fed from the condensate pump 60 is partially branched, isfed to a condensate cooler 12 via a condensate feed pipe 63, and coolsboiler exhaust gas discharged from a gas heat exchanger 11. Thecondensate temperature at the exit of the condenser 60 depends upon thevacuum level of the condenser, though assuming the vacuum level as 722mmHg Vac, the saturation temperature is about 33.1° C. and thecondensate can cool boiler exhaust gas discharged from the gas heatexchanger 11. If the gas temperature at the exit of the condensatecooler 12 is lowered, the gas temperature of exhaust gas flowing into acooling water-desalination apparatus 15 at the later stage is lowered.The condensate heated by the condensate cooler 12 flows into a deaerator65 via a condensate return pipe 64. The heat captured by the condensatecooler 12 produces an efficiency improvement effect for the entireplant. Further, by the condensate cooler 12, the exhaust gas temperatureat the exit of the gas heat exchanger 11 is lowered, thus the entrancedevice of a forced fan (FDF) 27 which will be described later is cooledto an allowable design temperature or lower.

The feed water discharged from the deaerator 65 is pressurized by thefeed water pump 66, flows down through the high-pressure feed waterheater 67, and is fed into the oxygen combustion boiler 1 as feed waterfrom the boiler feed water pipe 5. This feed water is heated again tosteam by the oxygen combustion boiler 1 and is fed to the steam turbine2.

Into the oxygen combustion boiler 1, coal fuel is input from a coal fuelfeed apparatus 7 via a fuel feed pipe 9. In the coal fuel, hydrogen 45,carbon 46, nitrogen 47, and sulfur 48 are included.

At the exit of an induction fan (IDF) 35, a part of the boiler exhaustgas is branched, and the branched boiler exhaust gas is permitted toflow down through a boiler exhaust gas recirculation duct 24 via aboiler exhaust gas recirculation damper 81 and recirculate to the oxygencombustion boiler 1. Namely, a boiler exhaust gas recirculation gassystem for returning the exit gas of the induction fan (IDF) 35 to theentrance of the forced fan (FDF) 27 is installed and the boiler exhaustgas is recirculated to the oxygen combustion boiler 1. The residualboiler exhaust gas flows on the side of a desulfurizer 14.

Further, in the boiler exhaust gas recirculation duct 24, oxygen 44 inair from the oxygen separator 6 flows via an oxygen feed damper 80 atthe exit of the oxygen separator and the oxygen feed pipe 8 and is mixedwith boiler recirculation gas. Namely, the oxygen injection place fromthe oxygen separator 6 is connected to the entrance of the forced fan(FDF) 27, thus the oxygen can be mixed with boiler exhaust gas from thecondensate cooler 12. In the oxygen separator 6, nitrogen 43 in the airis separated from oxygen 44 in the air.

A mixture of oxygen and boiler recirculation gas flows down through anentrance duct 26 of the forced fan (FDF) and is sucked into the forcedfan (FDF) 27. The mixed gas including oxygen is pressurized by theforced fan (FDF) 27, passes through an exit duct 28 of the forced fan(FDF), and enters the gas heat exchanger 11 to be heated. The mixed gasraised in temperature by the gas heat exchanger 11 passes through anexit duct 30 of the gas heat exchanger and is input into the oxygencombustion boiler 1 to burn coal.

Oxygen is oxidized in the oxygen combustion boiler 1, so that thecomponents in the exhaust gas of the oxygen combustion boiler 1 aremainly composed of carbon dioxide 53, steam 54, nitrogen oxide 55, andsulfur oxide 56. These boiler exhaust gas components flow into thedenitrification equipment 10 via an exit exhaust gas duct 31 of theoxygen combustion boiler. In the denitrification equipment 10, accordingto the chemical reaction formulas (1) and (2) indicated below, thenitrogen oxide 55 in the exhaust gas of the oxygen combustion boiler isdecomposed by the chemical reaction on ammonia, thus exit steam 57 ofthe denitrification equipment and exit nitrogen 58 of thedenitrification equipment are produced.

4NO+4NH₃+O₂→4N₂+6H₂O  (1)

2NO₂+4NH₃+O₂→3N₂+6H₂O  (2)

Exit boiler exhaust gas of the denitrification equipment 10 flows intothe gas heat exchanger 11 via an exit duct 32 of the denitrificationequipment.

Boiler exhaust gas discharged from an exit duct 33 of the gas heatexchanger and the condensate cooler 12 flows down through an entranceduct 34 of the dust collector. The boiler exhaust gas with dust removedby the dust collector (electric dust collector) 13 is induced andpressurized by the induction fan 35.

The sulfur oxide 56 in the exit exhaust gas of the oxygen combustionboiler becomes exit sulfur oxide 59 of the denitrification equipmentwithout being particularly affected. Furthermore, it becomes exit sulfuroxide 85 of the gas heat exchanger, flows down through the condensatecooler 12, the dust collector 13, and an induction fan (IDF) 35, andenters the desulfurizer 14 to be desulfurized. Here, the exit sulfuroxide 85 of the gas heat exchanger causes a chemical reaction on calciumcarbonate CaCO₃ 49 according to the following chemical reaction formula(3) and becomes calcium sulfate CaSO₄.2H₂O and carbon dioxide gas. Thecarbon dioxide gas becomes exit carbon dioxide 86 of the desulfurizertogether with exit carbon dioxide 68 of the gas heat exchanger and iscaptured by capture 16 of the carbon dioxide liquefier that will bedescribed later.

SO₂+2H₂O+CaCO₃+0.5O₂→CaSO₄.2H₂O+CO₂  (3)

The boiler exhaust gas components flowing through a desulfurizer exitduct 36 at the exit of the desulfurizer 14 are composed of only carbondioxide, steam, and nitrogen gas.

The boiler exhaust gas discharged from the desulfurizer 14 ispressurized by a pressurizing fan (BUF) 98 and is sent by the coolingwater-desalination apparatus 15. Non-condensable gas in the coolingwater-desalination apparatus 15 and steam are cooled simultaneously,thus the moisture in the gas is cooled to the steam saturationtemperature or lower to be captured. To the cooling water-desalinationapparatus 15, the cooling water 19 is fed through the cooling water feedpipe 18. The cooling water discharged from the coolingwater-desalination apparatus 15 passes through a cooling water returnpipe 20, becomes return cooling water 21, and comes out. The waterseparated by the cooling water-desalination apparatus 15 is pressurizedby a desalinated water take-out pipe 22 and a desalinated water transferpump 70 and is fed to a fresh water tank 72 to be stored. The storedfresh water passes through a feed water desalination apparatus 74 via anentrance pipe 73 of the feed water desalination apparatus and afterremoval of impurities in the fresh water, is fed to the condenser 60 aswater to supplement blow water with water-steam cycle water of the steamturbine 2 or feed water for water-steam cycle water during continuousoperation to be utilized.

In this embodiment, the exit gas temperature of the condensate cooler 12is lowered, thus the gas temperature of exhaust gas flowing into thecooling water-desalination apparatus 15 at the later stage is lowered,so that without increasing the amount of cooling feed water to thecooling water-desalination apparatus 15 and lowering the watertemperature, the moisture amount captured by the coolingwater-desalination apparatus 15 can be increased to three or four timesand it is a sufficient amount of water to supplement blow water withwater-steam cycle water of the steam turbine 2 or feed water forwater-steam cycle water during continuous operation.

To the coal fuel feed apparatus 7, from a low-temperature bypass damper75 of the gas heat exchanger, boiler recirculation gas includinglow-temperature oxygen is fed. Furthermore, from an exithigh-temperature damper 76 of the gas heat exchanger, boilerrecirculation gas including high-temperature oxygen is fed to the coalfuel feed apparatus 7. This gas including coal passes through the fuelfeed pipe 9 and is input to the oxygen combustion boiler 1, thus coalcombustion is executed.

High-purity nitrogen gas 52 discharged from the oxygen separator andexit nitrogen gas 23 of the carbon oxide liquefier are returned into theoriginal air.

At the time of start, the oxygen combustion boiler 1 is air-burned usingstarting fuel. To start the oxygen combustion boiler 1, via an airintake duct 25 and an air intake damper 82, air is permitted to flowinto the forced fan (FDF) 27 through the entrance duct 26 of the forcedfan (FDF). This air is pressurized by the forced fan (FDF) 27, thenpasses through the exit duct 28 of the forced fan (FDF), and enters thegas heat exchanger 11. By the gas heat exchanger 11, air is heated byboiler exhaust gas, flows down through the exit duct 30 of the gas heatexchanger, is conveyed to the oxygen combustion boiler 1 as combustionair, and burns the starting fuel (for example, gas oil, not drawn). Theboiler exhaust gas discharged from the oxygen combustion boiler 1 passesthrough the denitrification equipment 10, the gas heat exchanger 11, thecondensate cooler 12, and the dust collector 13, is sucked in andpressurized by the induction fan (IDF) 35. The pressurized boilerexhaust gas passes through the desulfurizer 14, flows down through thedesulfurizer exit duct 36 and a chimney entrance damper 96, enters achimney 97, and is discharged into the air.

After starting, if oxygen combustion is switched, by an operation ofclosing the chimney entrance damper 96 by opening an entrance damper 95of the cooling water-desalination apparatus, the boiler exhaust gas isswitched to the side of the cooling water-desalination apparatus. Theboiler exhaust gas flows on the side of the cooling water-desalinationapparatus entrance damper 95 and the moisture and carbon dioxide in theboiler exhaust gas are captured respectively by the coolingwater-desalination apparatus 15 and the carbon dioxide liquefier 16which are apparatuses on the downstream side. The captured moisture isstored once in the fresh water tank 72. Further, the captured carbondioxide is stored once in a carbon dioxide storage tank 17.

As mentioned above, this embodiment, using the oxygen combustion boiler,oxygen separator, fuel feed apparatus, steam turbine, steam turbinegenerator, denitrification equipment, gas heat exchanger, condensatecooler for cooling gas heat exchanger exit gas by condensate at the exitof the condenser which is a part of turbine steam cycle water, dustcollector, desulfurizer, cooling water-desalination apparatus, andcarbon dioxide liquefier, utilizing the characteristic that the maincomponents of exhaust gas of the oxygen combustion boiler aftercombustion are carbon dioxide gas and steam, cools and compresses theexhaust gas and captures simultaneously the moisture and carbon dioxidein the gas. Furthermore, this embodiment is equipped with a water feedsystem for utilizing the moisture captured from the boiler exhaust gasas cycle water of the steam-water cycle of the steam turbine. The steamfrom the oxygen combustion boiler is all used for power generation andfeed of a large amount of steam required by the water desalinationapparatus and carbon dioxide capture apparatus is never necessary.

According to this embodiment, in correspondence to the fuel kind burnedby the boiler (coal in this embodiment), from the fuel, not onlyelectric energy but also water and carbon dioxide can be obtainedsimultaneously in large quantities at a low cost by a method friendly tothe natural environment. Namely, from the exhaust gas system of theoxygen combustion boiler, sulfur oxides, nitrogen oxides, dust, andcarbon dioxide are never discharged into the atmosphere, so that steam,water, and carbon dioxide for power generation can be producedsimultaneously. Furthermore, the captured water can be utilized as steamcycle water of the steam turbine. Further, the oxygen combustion boiler,to output the same output, compared with a conventional general aircombustion boiler, does not need to suck in nitrogen gas in the air notcontributing to combustion into the boiler furnace, and generation of anitrogen oxide produced from nitrogen gas in the air is not caused, sothat an environment improvement effect is obtained. Not only fresh watergenerated by water desalination can be reused as steam cycle water ofthe steam turbine but also with respect to excessive moisture, in aregion lacking in water resources, practical use as industrial water anddrinking water can be expected.

Further, in the patent document 1, the boiler exhaust gas recirculationfan system is used, so that a recirculation fan for recirculating theboiler exhaust gas is necessary and an increase in the cost of equipmentand an increase in the fan power are caused. In this embodiment, theinduction fan (IDF) 35 and the forced fan (FDF) 27 are used forrecirculation, so that compared with the case of use of therecirculation fan, an effect of reducing the cost of equipment and poweris obtained.

Further, in the embodiment aforementioned, the exhaust gas dischargedfrom the desulfurizer 14 is pressurized by the pressurizing fan (BUF) 98and is sent to the cooling water-desalination apparatus 15, though thenecessary total head of the boiler exhaust gas fed to the coolingwater-desalination apparatus 15 is permitted to impose a burden on thehead of the induction fan, thus the pressurizing fan can be omitted.

Embodiment 2

FIG. 2 shows a second embodiment of the present invention of themultipurpose thermal power plant system using fuel like liquefiednatural gas (LNG) composed of the main components of carbon and hydrogenfree of a very small amount of sulfur and nitrogen as fuel of the oxygencombustion boiler 1. This embodiment is also a multipurpose thermalpower plant system for simultaneously capturing electric power, water,and carbon dioxide. For the same portions as those shown in FIG. 1, theexplanation will be omitted.

In this embodiment, the oxygen combustion boiler 1 burns LNG fed from aliquefied natural gas (LNG) fuel feed apparatus 77 and generate steam.Therefore, the oxygen combustion boiler 1 has a system constitution thatfrom the embodiment shown in FIG. 1, the denitrification equipment, ductcollector, and desulfurizer are removed.

To the oxygen combustion boiler 1, from the liquefied natural gas (LNG)fuel feed apparatus 77, LNG fuel composed of hydrogen 45 and carbon 46is input. Further, to the oxygen combustion boiler 1, mixed gas of theoxygen raised in temperature by the gas heat exchanger 11 and boilerrecirculation gas is input and the mixed gas burns the LNG fuel. LNG isoxidized in the oxygen combustion boiler 1, thus the exhaust gascomponents of the oxygen combustion boiler 1 are composed of mainlycarbon dioxide 53 and hydrogen 54 in the exhaust gas of the oxygencombustion boiler.

The boiler exhaust gas passes through the exit exhaust gas duct 31 ofthe oxygen combustion boiler and flows down into the gas heat exchanger11. The boiler exhaust gas is fed to the condensate cooler 12 via theexit duct 33 of the exhaust gas heat exchanger and is cooled by acondensate. If the exit gas temperature of the condensate cooler 12 islowered, the gas temperature to the cooling water-desalination apparatus15 at the later stage is lowered and a cooling effect is produced.Further, the condensate heated by the condensate cooler 12 passesthrough the condensate return pipe 64 and flows into the deaerator 65.The captured heat produces an efficiency improvement effect for theentire plant.

The boiler exhaust gas discharged from the condensate cooler 12 entersthe induction fan (IDF) 35. The boiler exhaust gas is induced andpressurized by the induction fan (IDF) 35, and then is fed to thecooling water-desalination apparatus 15. The boiler exhaust gas iscooled by the cooling water-desalination apparatus 15, thus the moisturein the gas is cooled to the steam saturation temperature or lower and iscaptured.

At the time of starting, similarly to Embodiment 1, the oxygencombustion boiler 1 is air-burned using starting fuel (for example, gasoil). The air-burned boiler exhaust gas passes through the gas heatexchanger 11 and the condensate cooler 12 and is sucked in andpressurized by the induction fan (IDF) 35. The pressurized boilerexhaust gas flows down through the chimney entrance damper 96, entersthe chimney 97, and is discharged into the air. After starting, ifoxygen combustion is switched, by an operation of closing the chimneyentrance damper 96 by opening the entrance damper 95 of the coolingwater-desalination apparatus, the boiler exhaust gas is switched to theside of the cooling water-desalination apparatus.

The moisture and carbon dioxide in the boiler exhaust gas are capturedrespectively by the cooling water-desalination apparatus 15 and thecarbon dioxide liquefier 16 which are apparatuses on the downstreamside. The captured moisture is stored once in the fresh water tank 72.Further, the captured carbon dioxide is stored once in the carbondioxide storage tank 17. High-purity exit nitrogen gas of the carbonoxide liquefier is returned into the original air.

According to this embodiment, similarly to Embodiment 1, incorrespondence to the fuel kind burned by the boiler (liquefied naturalgas (LNG) in this embodiment), from the fuel, not only electric energybut also water and carbon dioxide can be obtained simultaneously inlarge quantities at a low cost by a method friendly to the naturalenvironment.

Also in this embodiment, the induction fan (IDF) 35 and the forced fan(FDF) 27 are used for recirculation, so that compared with the case ofuse of the recirculation fan, an effect of reducing the cost ofequipment and power is obtained.

Further, as fuel of this embodiment, liquefied natural gas (LNG) isused, so that the pressure in the furnace of the oxygen combustionboiler generally using a negative pressure design can be changed to apositive pressure design and in this case, the head of the induction fanis permitted to impose a burden on the head of the forced fan (FDF) 27,thus the induction fan (IDF) 35 can be omitted and it is effective inreducing the cost of equipment.

Further, similarly to Embodiment 1, the necessary total head of theboiler exhaust gas fed to the cooling water-desalination apparatus 15 ispermitted to impose a burden on the head of the induction fan, thus thepressurizing fan can be omitted.

Embodiment 3

FIG. 3 shows a third embodiment of the present invention of themultipurpose thermal power plant system using fuel like hydrogen gascomposed of hydrogen free of a very small amount of sulfur and nitrogenas fuel of the oxygen combustion boiler 1. This embodiment is amultipurpose thermal power plant system for simultaneously capturingelectric power and water. For the same portions as those shown in FIG.1, the explanation will be omitted.

In this embodiment, the oxygen combustion boiler 1 burns hydrogen fedfrom a hydrogen fuel feed apparatus 78 and generates steam. Therefore,the oxygen combustion boiler 1 has a system constitution that from theembodiment shown in FIG. 1, the denitrification equipment, ductcollector, desulfurizer, and carbon dioxide liquefier are removed.

To the oxygen combustion boiler 1, from the hydrogen gas fuel feedapparatus 78, hydrogen 45 for fuel is input from the fuel feed pipe 9.Further, to the oxygen combustion boiler 1, mixed gas of the oxygenraised in temperature by the gas heat exchanger 11 and boilerrecirculation gas is input and the mixed gas burns the hydrogen.Hydrogen is oxidized in the oxygen combustion boiler 1, thus the exhaustgas components of the oxygen combustion boiler 1 are composed of mainlysteam 54.

The boiler exhaust gas passes through the exit exhaust gas duct 31 ofthe oxygen combustion boiler and flows down into the gas heat exchanger11. The boiler exhaust gas is fed to the condensate cooler 12 via theexit duct 33 of the exhaust gas heat exchanger and is cooled by acondensate. If the exit gas temperature of the condensate cooler 12 islowered, the gas temperature to the cooling water-desalination apparatus15 at the later stage is lowered. Further, the condensate heated by thecondensate cooler 12 passes through the condensate return pipe 64 andflows into the deaerator 65. The captured heat produces an efficiencyimprovement effect for the entire plant.

The boiler exhaust gas discharged from the condensate cooler 12 entersthe induction fan (IDF) 35. The boiler exhaust gas is induced andpressurized by the induction fan (IDF) 35, and then is fed to thecooling water-desalination apparatus 15. The boiler exhaust gas iscooled by the cooling water-desalination apparatus 15, thus the moisturein the gas is cooled to the steam saturation temperature or lower and iscaptured.

At the time of starting, similarly to Embodiment 1, the oxygencombustion boiler 1 is air-burned using starting fuel (for example, gasoil). The air-burned boiler exhaust gas passes through the gas heatexchanger 11 and the condensate cooler 12 and is sucked in andpressurized by the induction fan (IDF) 35. The pressurized boilerexhaust gas flows down through the chimney entrance damper 96, entersthe chimney 97, and is discharged into the air. After starting, ifoxygen combustion is switched, by an operation of closing the chimneyentrance damper 96 by opening the entrance damper 95 of the coolingwater-desalination apparatus, the boiler exhaust gas is switched to theside of the cooling water-desalination apparatus.

The moisture in the boiler exhaust gas is captured by the coolingwater-desalination apparatus 15. The captured moisture is stored once inthe fresh water tank 72.

According to this embodiment, similarly to the other embodiments, incorrespondence to the fuel kind burned by the boiler (hydrogen gas inthis embodiment), from the fuel, not only electric energy but also watercan be obtained simultaneously in large quantities at a low cost by amethod friendly to the natural environment.

Further, as fuel of this embodiment, hydrogen gas is used, so that thepressure in the furnace of the oxygen combustion boiler generally usinga negative pressure design can be changed to a positive pressure designand in this case, the head of the induction fan is permitted to impose aburden on the head of the forced fan (FDF) 27, thus the induction fan(IDF) 35 can be omitted and it is effective in reducing the cost ofequipment.

Further, similarly to Embodiment 1, the necessary total head of theboiler exhaust gas fed to the cooling water-desalination apparatus ispermitted to impose a burden on the head of the induction fan, thus thepressurizing fan can be omitted.

Embodiment 4

FIG. 4 shows a fourth embodiment of the present invention of themultipurpose thermal power plant system using fuel like carbon (char)composed of carbon free of a very small amount of sulfur and nitrogen asfuel of the oxygen combustion boiler 1. This embodiment is amultipurpose thermal power plant system for simultaneously obtainingsteam and carbon dioxide. For the same portions as those shown in FIG.1, the explanation will be omitted.

This embodiment burns carbon fed from a carbon fuel feed apparatus 79and generates steam. Therefore, this embodiment has a systemconstitution that from the embodiment shown in FIG. 1, thedenitrification equipment, duct collector, desulfurizer, and coolingwater-desalination apparatus are removed.

To the oxygen combustion boiler 1, from the carbon fuel feed apparatus79, carbon 46 for fuel is input via the fuel feed pipe 9. Further, tothe oxygen combustion boiler 1, mixed gas of the oxygen raised intemperature by the gas heat exchanger 11 and boiler recirculation gas isinput and the mixed gas burns the carbon. Carbon is oxidized in theoxygen combustion boiler 1, thus the exhaust gas component of the oxygencombustion boiler 1 is carbon dioxide 53 in the exit exhaust gas of theoxygen combustion boiler.

The boiler exhaust gas passes through the exit exhaust gas duct 31 ofthe oxygen combustion boiler and flows down into the gas heat exchanger11. The boiler exhaust gas is fed to the condensate cooler 12 via theexit duct 33 of the exhaust gas heat exchanger and is cooled by acondensate. If the exit gas temperature of the, condensate cooler 12 islowered, the gas temperature to the carbon dioxide liquefier 16 at thelater stage is lowered and an effect of improving the efficiency ofliquefying carbon dioxide is produced. The condensate heated by thecondensate cooler 12 passes through the condensate return pipe 64 andflows into the deaerator 65. The captured heat produces an efficiencyimprovement effect for the entire plant.

The boiler exhaust gas discharged from the condensate cooler 12 entersthe induction fan (IDF) 35. The boiler exhaust gas is induced andpressurized by the induction fan (IDF) 35 and then is fed to the carbondioxide liquefier 16. The boiler exhaust gas (carbon dioxide gas) iscompressed and cooled by the carbon dioxide liquefier 16, and is therebyliquefied.

At the time of starting, similarly to Embodiment 1, the oxygencombustion boiler 1 is air-burned using starting fuel (for example, gasoil). The air-burned boiler exhaust gas passes through the gas heatexchanger 11 and the condensate cooler 12 and is sucked in andpressurized by the induction fan (IDF) 35. The pressurized boilerexhaust gas flows down through the chimney entrance damper 96, entersthe chimney 97, and is discharged into the air. After starting, ifoxygen combustion is switched, by an operation of closing the chimneyentrance damper 96 by opening the entrance damper 94 of the carbondioxide liquefier, the boiler exhaust gas is switched to the side of thecarbon dioxide liquefier.

Carbon dioxide in the boiler exhaust gas is captured by the carbondioxide liquefier 16 that is an apparatus on the downstream side. Thecaptured carbon dioxide is stored once in the carbon dioxide storagetank 17.

According to this embodiment, similarly to the other embodiments, incorrespondence to the fuel kind burned by the boiler (carbon (char) inthis embodiment), from the fuel, not only electric energy but alsocarbon dioxide can be obtained simultaneously in large quantities at alow cost by a method friendly to the natural environment.

Further, as fuel of this embodiment, carbon (char) is used, so that thepressure in the furnace of the oxygen combustion boiler generally usinga negative pressure design can be changed to a positive pressure designand in this case, the head of the induction fan is permitted to impose aburden on the head of the forced fan (FDF) 27, thus the induction fan(IDF) 35 can be omitted and it is effective in reducing the cost ofequipment.

Further, similarly to Embodiment 1, the necessary total head of theboiler exhaust gas fed to the cooling water-desalination apparatus 15 ispermitted to impose a burden on the head of the induction fan, thus thepressurizing fan can be omitted.

What is claimed is:
 1. A multipurpose thermal power plant systemcomprising an oxygen combustion boiler, a steam turbine driven by steamgenerated by the oxygen combustion boiler, a generator driven by thesteam turbine, an oxygen separator for generating oxygen fed to theoxygen combustion boiler, a fuel feed apparatus for feeding fossil fuelcomposed of carbon, hydrogen, a small amount of sulfur, and nitrogen tothe oxygen combustion boiler, a denitrification equipment for removingnitrogen oxides in the exhaust gas of the oxygen combustion boiler, agas heat exchanger for performing heat exchange between the boilerexhaust gas and recirculation boiler exhaust gas including oxygen, acondensate cooler for cooling exhaust gas at an exit of the gas heatexchanger with a condensate of the steam turbine, a recirculation systemfor recirculating boiler exhaust gas at an exit of the condensate coolerto the oxygen combustion boiler, an oxygen injection system for feedingoxygen from the oxygen separator to the recirculation system, a dustcollector for removing dust from the exhaust gas at the exit of thecondensate cooler, a desulfurizer for removing sulfur in boiler exhaustgas from the dust collector, a cooling water-desalination apparatus forproducing water by cooling boiler exhaust gas from the desulfurizer, acarbon dioxide liquefier for obtaining carbon dioxide by compressingboiler exhaust gas at an exit of the cooling water-desalinationapparatus, a carbon dioxide storage tank for storing liquefied carbondioxide obtained by the carbon dioxide liquefier, a fresh water tank forcapturing water generated by the cooling water-desalination apparatus,and a water feed system for feeding water of the fresh water tank to thesteam turbine system as steam cycle water of the steam turbine.
 2. Amultipurpose thermal power plant system comprising an oxygen combustionboiler, a steam turbine driven by steam generated by the oxygencombustion boiler, a generator driven by the steam turbine, an oxygenseparator for generating oxygen fed to the oxygen combustion boiler, afuel feed apparatus for feeding fossil fuel like liquefied natural gascomposed of carbon and hydrogen to the oxygen combustion boiler, a gasheat exchanger for performing heat exchange between the boiler exhaustgas and recirculation boiler exhaust gas including oxygen, a condensatecooler for cooling exhaust gas at an exit of the gas heat exchanger witha condensate of the steam turbine, a recirculation system forrecirculating boiler exhaust gas at an exit of the condensate cooler tothe oxygen combustion boiler, an oxygen injection system for feedingoxygen from the oxygen separator to the recirculation system, a coolingwater-desalination apparatus for producing water by cooling boilerexhaust gas from the condensate cooler, a carbon dioxide liquefier forobtaining carbon dioxide by compressing boiler exhaust gas at an exit ofthe cooling water-desalination apparatus, a carbon dioxide storage tankfor storing liquefied carbon dioxide obtained by the carbon dioxideliquefier, a fresh water tank for capturing water generated by thecooling water-desalination apparatus, and a water feed system forfeeding water of the fresh water tank to the steam turbine system assteam cycle water of the steam turbine.
 3. A multipurpose thermal powerplant system comprising an oxygen combustion boiler, a steam turbinedriven by steam generated by the oxygen combustion boiler, a generatordriven by the steam turbine, an oxygen separator for generating oxygenfed to the oxygen combustion boiler, a fuel feed apparatus for feedinghydrogen fuel to the oxygen combustion boiler, a gas heat exchanger forperforming heat exchange between the boiler exhaust gas andrecirculation boiler exhaust gas including oxygen, a condensate coolerfor cooling exhaust gas at an exit of the gas heat exchanger with acondensate of the steam turbine, a recirculation system forrecirculating boiler exhaust gas at an exit of the condensate cooler tothe oxygen combustion boiler, an oxygen injection system for feedingoxygen from the oxygen separator to the recirculation system, a coolingwater-desalination apparatus for producing water by cooling boilerexhaust gas from the condensate cooler, a fresh water tank for capturingwater generated by the cooling water-desalination apparatus, and a waterfeed system for feeding water of the fresh water tank to the steamturbine system as steam cycle water of the steam turbine.
 4. Amultipurpose thermal power plant system comprising an oxygen combustionboiler, a steam turbine driven by steam generated by the oxygencombustion boiler, a generator driven by the steam turbine, an oxygenseparator for generating oxygen fed to the oxygen combustion boiler, afuel feed apparatus for feeding fossil fuel composed of carbon to theoxygen combustion boiler, a gas heat exchanger for performing heatexchange between the boiler exhaust gas and recirculation boiler exhaustgas including oxygen, a condensate cooler for cooling exhaust gas at anexit of the gas heat exchanger with a condensate of the steam turbine, arecirculation system for recirculating boiler exhaust gas at an exit ofthe condensate cooler to the oxygen combustion boiler, an oxygeninjection system for feeding oxygen from the oxygen separator to therecirculation system, a carbon dioxide liquefier for obtaining carbondioxide by compressing boiler exhaust gas from the condensate cooler,and a carbon dioxide storage tank for storing liquefied carbon dioxideobtained by the carbon dioxide liquefier.